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Elements vs Compound

Elements First letter of element symbol is always capitalized Only have one capitalized letter. Compounds Combination of elements Can recognize by how many capital letters (2 or more). Elements vs Compound. H 2 O NaCl Fe O2 Ba(OH) 2 K. Law of Definite Proportions.

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Elements vs Compound

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  1. Elements First letter of element symbol is always capitalized Only have one capitalized letter Compounds Combination of elements Can recognize by how many capital letters (2 or more) Elements vs Compound H2O NaCl Fe O2 Ba(OH)2 K

  2. Law of Definite Proportions • Regardless of amount of compound we have, the compound will always be comprised of the same elements in the same proportions by mass % by mass = mass of element mass of compound x 100

  3. 20 grams from a sugar bag

  4. 500 grams from Sugar Cane

  5. Let’s Compare Are they the same compound????

  6. Compounds with same mass proportions must be the same compound • Compounds with different mass proportions  must be different compounds

  7. Law of Definite Proportions Practice I 1. If hydrogen composes 11% of a 100 gram sample of water, what is the mass of the hydrogen in the sample?

  8. 2. If one gram of hydrogen reacts completely with 19. g of fluorine, what is the percent by mass of hydrogen in the compound that is formed?

  9. 3. If 3% of a 100 g HCl solution is hydrogen, what is the mass of chlorine in the sample?

  10. 4. A 78.0 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?

  11. 5. If 40% of a 300 g NaCl solution is sodium, what is the mass of the sodium present in the sample?

  12. Law of Definite Proportions Practice II 1. Sodium has an atomic mass of 23 amu’s and chlorine has an atomic mass of 25 amu’s. In the compound NaCl, what is the % composition by mass of sodium?

  13. 2. Sulfur composes 33% of the compound H2SO4. What would be the mass of sulfur in a 500 gram sample of H2SO4?

  14. 3. If 32 grams of sulfur reacts completely with 32 grams of oxygen, what is the mass of sulfur in 800 g of SO2?

  15. 4. An 800 g sample of an unknown substance contains 121 g of hydrogen. What is the % composition of hydrogen by mass in the substance?

  16. 5. If 28.8% of a 600 gram sample of NaBr is sodium, what is the mass of the sodium present in the sample?

  17. How many grams of sodium are contained in a 500 gram sample of sodium chloride (NaCl)? • Na = 23.0  periodic Table • Cl = 35.4  periodic Table • Total= Na + Cl = 23.0 + 35.4 = 58.4 g • % Na = (23 / 58.4) * 100 = 39.38% • 500 g * 39.38% = 500 * (39.38/100) = 197 g

  18. 1. Sodium has an atomic mass of 23 amu’s and chlorine has an atomic mass of 25 amu’s. In the compound NaCl, what is the % composition by mass of sodium?

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